(1) Field of the Invention
The present invention relates to a power transducer and more particularly to an internal structure thereof.
(2) Description of the Related Art
An inverter, which is a form of power transducers, is frequently used as a device that controls a speed of an industrial alternating current motor. For example, a power transducer is implemented in home electric appliances, vehicles or the like. In addition to the mounting to home electric appliances and vehicles, a power transducer may be mounted on a control board. In such cases, spaces where the power transducers are to be mounted are restricted in general. Thus it is strongly requested to reduce the size of the power transducers.
A typical one of the power transducers drives a power element (power semiconductor device) such as an insulated gate bipolar transistor (IGBT) as a switching element to variably control voltages and frequencies. In recent years, a semiconductor module having incorporated therein a peripheral circuit such as a protective circuit has often been used to reduce the size of the power transducer. Such a semiconductor module is so-called an intelligent power module (IPM).
JP-A-2003-332526 discloses a power module in order to reduce the size of a power transducer. As described in paragraphs 0014 and 0015 of JP-A-2003-332526, a wiring board for the power transducer is divided into a power source board (provided for a large-current circuit) and a control board (provided for a minute electric current circuit). In this case, only the control board is located in the vicinity of an upper surface of a main circuit module. FIG. 15 of JP-A-2003-332526 shows an example of the wiring board. With the thus divided wiring board, a thin copper foil printed wiring board can be used as the control board (wiring board provided for a control circuit) in which a current with a small amount flows. Thus, the size of the wiring board can be suppressed and thereby the area of a region in which to mount the power module is reduced.